Electrocardiogram (ECG)-gated cardiac magnetic resonance imaging (MRI) is the gold standard for volumetric evaluation of patients. Cardiovascular Magnetic Resonance imaging (CMR), sometimes known as cardiac MRI, is a medical imaging technology for the non-invasive assessment of the function and structure of the cardiovascular system. It is derived from, and based on, the same basic principles as magnetic resonance imaging (MRI) but with optimization for use in the cardiovascular system. These optimizations are principally in the use of ECG gating and rapid imaging techniques or sequences. By combining a variety of such techniques into protocols, key functional and morphological features of the cardiovascular system can be assessed.
Imaging of the heart allows for mathematical expressions defining flow of blood in and out of the heart. Cardiac imaging uses visually enhanced mathematics of the folding and unfolding of the myocardium focused on a single cardiac cycle.
Clinically, ejection fraction (EF) is used as a surrogate for function. Ejection fraction is the fraction of outbound blood pumped from the heart with each heartbeat. It is a general measure of a person's cardiac function. Ejection fraction is typically low in patients with systolic congestive heart failure.